Method of cooling indirectly



Oct. 9, 1934. SCHLUMBOHM 1,975,868

METHOD OF COOLING INDIRECTLY Filed Feb. 9. 1931 2 Sheets-Sheet 1 Oct. 9, 1934. P. SCHLUMBOHM METHOD OF COOLING INDIRECTLY 2 Sheets-Sheet Filed Feb. 9, 1931 Patented Oct. 9, 1934 UNITED STATES PATENT OFFICE METHOD OF COOLING INDIRECTLY Application February 9, 1931, Serial No. 514,598

. In Germany February 10, 1930 6 Claims.

My invention relates to the method of cooling indirectly by the aid of a secondary refrigerant which becomescondensed and evaporated in a circuit by condensing the vapors on a wall cooled by the primary refrigerant.

The chief object of my invention is to control the temperature effect of the evaporating secondary refrigerant. Although the process of cooling indirectly is old, this point never was considered sufliciently. It is not suflicient to provide valves for closing the connection tubes between the condenser and the evaporator. My invention goes to the thermostatic control of the circuit, shutting those valves and opening them fully automatically. This was never applied before in the circuit of a secondary refrigerant. The only suggestion made for the circuit of a secondary refrigerant was to keep a certain amount of air inside of the evaporator and condenser system in order to use carbon dioxide ice without danger. This is a very primitive method. Nobody would buy a high-powered car and use it in first gear only. That amount of air makes the system work with a constant brake instead of allowing the system to work at full speed when it is supposed to create cold in the evaporator, and blocks the system entirely when too dangerous a temperature is reached in the evaporator.

The new method is to be applied in connection.

with carbon dioxide as a primary refrigerant or with brine as a primary refrigerant, this brine being used in a central cooling system flowing through various condensers, or with any other primary refrigerant of very low temperature, which is to be used to maintain a higher temper ature.

Another object of my invention is to regulate the circuit of the secondary refrigerant thermostatically. Such a full automatic control is known on the circuit of a primary refrigerant. In those systems where a primary refrigerant creates the cold, such a thermostat has to start or stop the motor of the compressor or the heating and cooling of an absorber system. In the system of indirect cooling t e thermostat has to throttle and to open the ci cuit of the secondary refrigerant. According to my invention the thermostat is controlled by the temperature of the secondary refrigerant. This means that the circuit of the secondary refrigerant is stopped automatically if the temperature of the secondary refrigerant reaches a certain low degree, for instance, 20 degrees C., and that the circuit is re-opened if the temperature of the secondary refrigerant; goes above that certain degree, by warmth which penetrates into the evaporator.

My invention creates a temperature transformer which transforms the dangerous low temperature of the carbon dioxide ice into any wanted higher temperature, without any caloric loss. I might state that by this process a carbon dioxide ice refrigerator can work just as precisely as 'a mechanical refrigerator so far as maintaining a constant harmless temperature, especially for pre- 65 serving foods, is concerned.

Coming to details, I refer to the enclosed drawings without, of course, limiting the scope of my invention to these exemplifications.

Fig. 1 shows, partly in section, partly in side elevation, a unit for indirect cooling with carbon dioxide ice, fitted with a thermostatically controlled valve.

Fig. 2 illustrates, in vertical section, such a unit, thermostatically controlled by the temper- 76 ature of the secondary refrigerant, this unit being placed in the upper part of a refrigerator box, or a cooling room which is shown in part.

Fig. 3 shows a thermostatically controlled unit, placed inside of a refrigerator box, this refrig- 80 erator box standing on the floor of a room which is to be seen in part on the drawing.

The unit shown in Fig. 1 comprises a container 1 for the carbon dioxide ice 2, this container being double walled as shown at 4, 5, the space 3 be- 86 tween the two walls forming the condenser for the secondary refrigerant, and an evaporator 10 for the secondary refrigerant, and a connection tube 64: between said condenser 3 and said evaporator 10. The tube So can be shut off by a valve 13b, this 90 valve being controlled thermostatically. The parts 13c, 130. (an elastic wall), 13d, and l3e form the mechanism which moves the valve 13b, under the influence of a thermostat. This thermostat itself is not shown in the drawings. It is under-' stood that it is connected with a solenoid 13d by electric wires l3e. The thermostat can be placed at a desired distance from the unit. if the temperature of the room is to influence the movement of valve 13b.

A more specific aim of my invention is to place .the thermostat inside of the evaporator, thus avoiding too low temperatures in the evaporator. This is shown in Fig. 2. The container 1 for the carbon dioxide ice 2 is the same as in 10 Fig. 1. The evaporator 10 also is double walled and is mounted in horizontal position. The vapors of the secondary refrigerant ll'pass through the tube 6 into the condenser 3. The liquefied vapors flow back to the evaporator 10, passing 11 is a she dipping into the secondary refrigerant 11. An elastic wall or diaphragm 13 is connected by a rod 13' to a valve 13a which is normally held against its seat by a contracting coil spring 14a connected to the diaphragm. The valve 136 is controlled by the vapor pressure of the thermostatic liquid inside the tube 14, which is sealed at both ends, the lower end dipping into the refrigerant 11. This vapor pressure increases as the temperature of the secondary refrigerant 11 'rises; and when this temperature reaches a predetermined point, the vapor pressure in tube 14 pushes the diaphragm 13 to the right (as viewed in Fig. 2) and thereby unseats the valve 13a 'to the elastic wall 13. In the case illustrated in Fig. 2, the temperature of a refrigerator box 22 can be controlled, also, by a second thermostat, which only indirectly influences the circuit of the secondary refrigerant. The unit for this circuit is placed inside of a chamber 16 through which the air of the cooling room 22 passes. This air current can be stopped by shutting the outlets 18 of the chamber with a thermostat 20, 21, for

instance, of the bi-metal type. The advantage of this combination of two theremostats is found in the fact that the making of ice cream in the bowls 8 is not stopped after the temperature of the cooling room has. gone down sufliciently.

Another improvement made by my invention is shown in Fig. 3. The unit for the indirect cooling process is nearly the same as that of Fig. 2. The only difference is the method of shutting off the tube 6. In Fig. 3 this is done by a mercury valve 15,- which is a U-shaped tube arranged to receive the open downward extension 12 of tube 6. There are various possibilities for making a mercury valve. Either the tube 6 can constantly dip into a certain column of mercury, this column forming a set resistance, or, as shown in Fig. 3, the tube 6 dipsinto the mercury (which in this case is the filling of a manometer) if the temperature of the secondary refrigerant 11 falls to a certain degree bon dioxide ice with a lid 25, fitted with a tube 26.

to guide away the gaseous carbon dioxide which is formed by the evaporation of the carbon dioxide ice. As it is the aim of the present invention to avoid dangerous temperatures in the cooling room, one has to consider this very cold gas,

too, and not only the solid carbon dioxide ice. For this purpose the cold gases are prevented from having direct contact with the cooling room.

As illustrated in Fig. 3, the tube 26 forms a heat exchanger with a surrounding tube 27. Outside air is cooled when passing through this tube 27, the air passing through the tube due to the influence of a'thermosiphon effect. The cooled air enters the cooling room through the tube 30. This way of the cold carbon dioxide gas is through the narrow tube 7. The thermostat 14 superior, in its economy, to the usual methods, because the gas is warmed up to the temperature of the outside air and not only, as usual, up to the temperature of the cooling room. The moisture of the air is condensed in the tube 27.

The condensed water enters a tube 29, forming a liquid trap to shut oif the tube 27 on the under side. I am adding to this arrangement, described and illustrated above, the improvement of guiding the tube 26 into the upper part of the room on the floor of which the refrigerator box is standing. This is a very simple and effective way of taking away the poisonous effect of the evolved carbon dioxide. It is known that this poisonous effect depends on the concentration of the carbon dioxide, beginning at a concentration of 4%. Our dry ice refrigerators, in which the gaseous carbon dioxide enters the cooling room, will certainly have this poisonous concentration, and even a higher one. By guiding the carbon dioxide, separated from the air of the cooling room, to the upper part of a living room, or a kitchen, this gas becomes diluted on its way down to the breathing zone of the persons in that room.

In this way a completely indirect cooling is effected, which at the same time avoids any too low temperatures, due to the thermostatic control.

.I have herein shown and described several practiwl constructions of my present improvements, butit will be apparent that the construction is susceptible of embodiment in various other alternative forms, and I therefore reserve the privilege of resorting to all such legitimate changes as may be fairly embodied within the spirit and scope of the invention as claimed in the appended claims.

What I claim is:

1. Cooling apparatus comprising the combination of a closed receptacle containing dry ice and located in a room to be cooled, a tube extending from said receptacle for the passage of carbon dioxide gas, a pipe surrounding said tube and spaced therefrom, said pipe being open at one end to the outside air and at the other end to the air in the room, whereby the warm outside air is cooled in the space between said tube and pipe and is discharged into the room, and means for discharging the moisture formed in said cooling space by the cooled air.

2. Cooling apparatus comprising a condenser adapted to hold a primary refrigerant and an evaporator adapted to hold a vaporizable secondary refrigerant, an outlet pipe connecting said evaporator with said condenser for the flow of vapor from the former to the latter, a return pipe connecting the condenser with the evaporator for the flow of condensed vapors to the evaporator, a. valve in said outlet pipe for controlling the flow of vapors, and a thermostat directly controlled by the temperature of the secondary refrigerant for operating said valve.

3. Cooling apparatus comprising a compartment to be cooled, a box located in said compartment and adapted to communicate therewith through at least one opening,- a refrigerating device mounted in said box, said device comprising a container for a vaporizable primary refrigerant and a second container for a vaporizable secondary refrigerant, said first container forming a condenser and the second container forming an evaporator, pipe connections between the two containers whereby the vapors of the secondary refrigerant circulate through the condenser and are returned as condensed liquid to the evaporator, means directly controlled by the temperature of the secondary refrigerant for automatically controlling the passage of vapor from the evaporator to the condenser, the vapors of said primary refrigerant being adapted to cool the inside of said box and thereby retard the evaporation of the primary refrigerant, a valve for controlling the opening between said box and compartment, and thermostatic means in said compartment for operating said valve, the vapor pressure in said box being greater than the pressure of the air in the compartment when said valve is opened, whereby infiltration of air into said box is prevented.

4. In cooling apparatus, the combination of a chamber to be cooled, an evaporator arranged in said chamber and containing a vaporizable refrigerant, an outlet pipe and a return pipe connected to said evaporator, a condenser to which said outlet pipe and return pipe are connected for the circulation of said refrigerant, said condenser being contained in said cooling chamber, and a mercury valve arranged in said outlet pipe and controlled by the vapor pressure in said pipe, said valve comprising a reservoir of mercury exposed to the temperature of said cooling chamher.

5. In cooling apparatus, the combination of an evaporator containing a vaporizable refrigerant, an outlet pipe and a return pipe connected to said evaporator, a condenser to which said outlet pipe and return pipe are connected for the circulation of said refrigerant, a valve in said outlet pipe, and a thermostatic device for controlling said valve, said device including a sealed tube containing a vaporizable liquid and dipping into said refrigerant, and an elastic member controlled by the vapor pressure in said sealed tube, said elastic member being connected to said valve, which is thus controlled in accordance with the temperature of said refrigerant to control the flow of vapor through said outlet pipe from the evaporator to the condenser.

6. In cooling apparatus, the combination of a double-walled receptacle containing a primary refrigerant, the space between the walls of said receptacle constituting a condensing chamber cooled by said primary refrigerant, an evaporator locatedin a room to be cooled and .containing a vaporizable secondary refrigerant, an outlet pipe connecting said evaporator and condensing chamber for the flow of vapors of said secondary refrigerant from the evaporator into the condenser chamber, a valve in said pipe connection for controlling the flow of said secondary refrigerant, and a thermostat directly controlled by the temperature of the secondary refrigerant for operating said valve, whereby the flow of said secondary refrigerant from the evaporator into the condenser chamber is automatically controlled in accordance with the temperature of the secondary refrigerant and independently of the room temperature, and a valveless return pipe between the condensing chamber and the evaporator for the free passage of the condensed vapors back to the evaporator.

PETER SCHLUMBOHM. 

